Throughout this description various publications are cited as representative of related art. For the sake of simplicity, these documents will be referred by reference numbers enclosed in square brackets, e.g. [x]. A complete list of these publications ordered according to the reference numbers is reproduced in the section entitled “List of references” at the end of the description. These publications are incorporated herein by reference.
Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems are promising solutions for next generation Wireless Local Area Network (WLAN) system thanks to the high data rate achievable. The OFDM technique is a promising method for high data rate communication systems due to its simple implementation via FFT and robustness against frequency selective fading channels. In a spatial multiplexing MIMO system, high data rate transmission is achieved by de-multiplexing the data sequence into N sub-streams that are transmitted through N antennas. Thus, MIMO-OFDM systems can provide high performance and reliable transmission.
The introduction of more antennas at the receive side involves a remarkable computation burden related to the extraction of the Log-Likelihood Ratios (LLR) from the received signal. This applies i.a. to the computation of the A-Posteriori Probabilities (APPs), which is very complex and whose computational complexity increases with pN, where p is the number of constellation points.
Therefore, typically only suboptimal techniques are used when p is large. An example of such a suboptimal technique is disclosed in [1].
Other solutions are based on multilevel coding for multiple-antenna systems. For example, [2] presents a comparison among different schemes.